A reaction in which an olefinic compound having a carbon-carbon double bond is reacted with carbon monoxide and hydrogen in the presence of a rhodium catalyst comprised of a rhodium compound and a phosphorous compound to be converted into an aldehyde is referred to as a hydroformylation reaction, and a method for producing an aldehyde using this reaction is of a high industrial value.
A compound having an ethylenic double bond on an end of the molecule is subjected to a hydroformylation reaction to generate a linear aldehyde and a branched aldehyde. Further, in some cases, isomers formed by isomerization of double bonds and aldehydes formed by hydroformylation of the isomers are by-produced.
The catalytic activity, the linear aldehyde selectivity, and the production ratio of linear aldehydes to branched aldehydes in the hydroformylation reaction vary depending on all the reaction conditions for hydroformylation, such as a reaction temperature, the compositional ratio of a mixed gas including carbon monoxide and hydrogen, the pressure of the mixed gas, the type and the use amount of a solvent, the structure of a terminal olefin compound, and the type of a phosphorous compound constituting a rhodium catalyst, for example. In particular, from the viewpoints that the type of the phosphorous compound constituting a rhodium catalyst significantly changes the electronic state of a rhodium atom, which is a central atom in the rhodium catalyst, and the steric structure in the periphery of a central rhodium metal in a rhodium complex intermediate which is a genuine active species of the rhodium catalyst, it has been known that the effects on a catalytic activity, a linear aldehyde selectivity, and a production ratio of linear aldehydes to branched aldehydes are significant (see NPLs 1 and 2).
Rhodium is expensive, and thus, in order to carry out a hydroformylation reaction in an industrially advantageous manner, it is important to achieve a decrease in the amount of rhodium to be used due to an improved catalytic activity; improve an aldehyde selectivity; and control the production ratio of linear aldehydes to branched aldehydes to a desired range at the same time so as to reduce the production cost in a plant for aldehydes. Further, various bisphosphites have been developed and have been reported in order to achieve such purposes.
On the other hand, a method for producing a linear dialdehyde by subjecting a linear olefinic compound each having an ethylenic double bond on an end of the molecule and an aldehyde group (hereinafter referred to as a linear unsaturated aldehyde in some cases) to hydroformylation has been known.
For example, the production ratios of linear dialdehydes (1,9-nonanedial; hereinafter referred to as NL) to branched dialdehydes (2-methyl-1,8-octanedial; hereinafter referred to as MOL) and the dialdehyde selectivity in a hydroformylation reaction of 7-octen-1-al using a bisphosphite having a specific structure, typically bisphosphite A, bisphosphite B, bisphosphite C, or the like as shown below, have been disclosed (see PTL 1).
Specifically, it is shown that in a case of using the bisphosphite A, an dialdehyde with NL/MOL=85.1/14.9 was obtained with a selectivity of 97.0%; in a case of using the bisphosphite B under the same conditions, an dialdehyde with NL/MOL=79.8/21.2 was obtained with a selectivity of 97.0%; and in a case of using the bisphosphite C under the same conditions, an dialdehyde with NL/MOL=79.7/20.3 was obtained with a selectivity of 97.7%.

Furthermore, in PTL 1, the stability of bisphosphite is disclosed. Specifically, it is shown that in a case of adding 100 mg (0.102 mmol) of bisphosphite A to 100 ml of toluene containing 70 ppm of water (0.337 mmol as water) (condition under which water is present at 3.3 molar times with respect to bisphosphite A), followed by carrying out a treatment at 125° C. under a nitrogen atmosphere, the residual rate of the bisphosphite A after 3 hours is 70%.